Thenyl quaternaries of certain thiazole intermediates for cyanine dyes



United States Patent 3,136,772 THENYL QUATERNARIES OF CERTAIN THIA- ZOLEINTERMEDIATES FOR CYANINE DYES Henry G. Derbyshire, Chenango Forks,N.Y., assignor to General Aniline & Film Corporation, New York, N.Y., acorporation of Delaware No Drawing. Filed Feb. 8, 1957, Ser. No. 638,9243 Claims. (Cl. 260-302) The present invention relates to cyclammoniumsalts in which the heterocyclic nitrogen atom contains ana-thienylmethyl group, sensitizing dyes derived therefrom, and silverhalide emulsions sensitized with such dyes.

The reaction of alkylating agents, e.g., alkyl halides, withheterocyclic nitrogenous bases to produce quaternary salts useful asintermediates for the preparation of sensitizing dyes has long beenknown to the photographic art.

It has now been discovered that new and valuable sensitizing dyes can beobtained from cyclammonium salts having an a-thienylmethyl group on thequaternary nitrogen atom. These quaternary salts can be reacted withcyclammonium quaternary salts containing a reactive group on thea-carbon atom to produce, inter alia, monoor polymethine cyanine dyeswhich are powerful sensitizers for silver halide emulsions.

Said cyclammonium salts, their preparation, dyes derived therefrom andsilver halide emulsions sensitized with said dyes constitute thepurposes and object of my invention.

The cyclammonium salts contemplated herein are readily prepared byreacting any heterocyclic base usual in preparing cyanine dyes, e.g.,quinoline, benzothiazole, naphthothiazole, thiazoline, thiazole,benzoselenazole, benzoxazole, indolenine, pyridine, benzimidazole, andthe like with a-thienylrnethyl halide, e.g., a-thienylmethyl bromide,and isolating the resulting quaternary salts in the usual manner.

The new cyclammonium salts may be represented by the following generalformula:

(I) x z wherein m is an integer of from 1 to 2, Z represents thenon-metallic atoms necessary to complete a 5- or 6-membered heterocyclicring of the type commonly encountered in cyanine dyes, such asquinoline, benzothiazole, naphthothiazole, thiazoline, thiazole,benzoselenazole, benzoxazole, indolenine, pyridine, benzimidazole andthe like, R is alkyl such as methyl, ethyl, propyl, butyl, and the like;aralkyl, i.e., benzyl, phenethyl and the like; and alkylmercapto group,i.e., methylmercapto, ethylmercapto, propyhnercapto, and the like; anarylmercapto group, i.e., phenylmercapto, a-naphthylmercapto, and thelike; and X is an anion such as a halide, alkylsulfate, or ap-toluenesulfonate.

The cyclammonium salts formulistically represented above may beconverted to sensitizing dyes having the following generalconfiguration:

using techniques well known to the art, such as heating said salts inthe presence of acid binding agents such as pyridine, triethylamine, andthe like with a cyclammonium quaternary salt containing a reactive groupon the carbon atom at the 2- or 4-position of the heterocyclic ring suchas a halogen atom, i.e., chlorine, bromine, or the like, a thioethergroup, a thioketo group, a B-anilino vinyl group, or the like.

In the above general formula for the sensitizing dyes, Y is alkyl suchas ethyl, methyl, propyl, butyl, etc., aralkyl, i.e., benzyl, phenethyl,etc., carboxyalkyl such as carboxyethyl, carboxypropyl, etc., oru-thienylmethyl, at least one Y being a-thienylmethyl, L is a methinegroup, i.e., =CHCR"=, wherein R" represents alkyl, i.e., methyl, ethyl,propyl, etc., Z represents the non-metallic atoms necessary to completea 5- or =6-membered heterocyclic ring of the type commonly encounteredin cyanine dyes such as quinoline, benzothiazole, naphthothiazole,thiazoline, thiazole, benzoselenazole, benzoxazole, indolenine,pyridine, benzimidazole, and the like, X is an anion as above, and nrepresents a whole number from 1 to 8.

This invention is illustrated in greater detail by the followingexamples although it is to be understood that said examples in no wayrestrict the present invention.

EXAMPLE I a-Trienylmethyl Bromide wThienylmethyl bromide is prepared byan adaptation of a method described in JACS, vol. 70, 42-48 (1948),which is as follows:

U H0110 EB. U OH.B. 11,0

40 grams thiophene and 34 mls. 48% HBr were mixed together at 5-l0 C.With vigorous stirring during the course of /2 hour, 50 mls. of 37%formaldehyde (H O) were added. The mixture was stirred /2 hour longer at5-10 C. The cloudy white yellow oil was ether extracted with three 50ml. portions of ether. The ether extracts were combined, washedwith'water, then sodium bicarbonate solution, and finally dried overanhydrous sodium sulfate. After solvent evaporation, the brown oilresidue was distilled at reduced pressure. The fraction boiling at 65-90C. at 4-8 mm. pressure was collected and used in the subsequentquaternation reactions.

triturated with ether, filtered, washed with ether, and then usedimmediately in the dye synthesis.

EXAMPLE III 3 Ethyl 4',5,6 Trimethyl 3 (a Thienylmethyl)Oxathiazolocarbocyanine Iodide 1.0 gram of the above prepared thiazoliumsalt from Example II, and 1.3 grams 2-(5-acetanilidovinyl)-3-ethyl-5,6-dimethylbenzoxazolium iodide were stirred together in 20 mls. ofisopropyl alcohol. The system was heated to boiling with constantagitation and 1 ml. triethylamine was added. Boiling and stirring werecontinued until all the starting materials were dissolved; then thereaction vessel was allowed to cool slowly to room temperature. Brassymetallic crystals of dye separated on the walls of the tube. The productwas removed by filtration, washed with cold isopropyl alcohol, andrecrystallized from 70 mls. hot methyl alcohol.

The melting point was 220223 C., and the absorption maximum in methanolwas 524 mg.

The dye, when coated in a gelatin silver halide emulsion, extended therange of sensitization to 590 me with a strong maximum at 555 III/L. Thepresence of the uthienylmethyl substituent increases sensitizingefiiciency of this dye. Simple alkyl substituted dyes sensitize the sameemulsion 50l00% less. The a-thienylmethyl group also causes abathochromic shift in dye absorption when substituted for a methylgroup.

14.9 grams of Z-methylbenzothiazole and 17.7 grams of m-thienylmethylbromide were stirred together on a steam bath for 20-minutes after whichtime a yellow solid had formed. The product was then dissolved iniso-propyl alcohol. On cooling to C., white crystals of the OL-thienylrnethyl quaternary salt were obtained; yield 18.0

grams.

2.0 grams of the above Z-methyl-a-thienylmethylbenzothiazolium bromide,5 mls. of ethyl orthoformate and mls. of pyridine were refluxed for 2minutes. At the end of this time, purple crystalsof dye with a metallicreflex had separated out on the walls of the reaction vessel. The crudedye was filtered oil, washed free of pyridine with cold iso-propylalcohol and crystallized from 100 mls. of methyl alcohol. Thecrystallized dye was filtered, washed with dry ether and dried at 65 C.The melting point was 220-223 C.

EXAMPLE V 9 Ethyl 3 Methyl 3' (a-Thienylmethyl) 4,5-Benzothiacarbocyanine Iodide l thiazolium iodide were dissolved in 10mls. of boiling isopropyl alcohol. 2 mls. of triethylamine were nextadded and the mixture boiled vigorously until a considerable quantity ofmetallic dye crystals had formed on the walls of the reaction vessel.After cooling to 0 C., the crude dye was filtered oif, washed withwater, then ether and boiled up with 250 mls. of methyl alcohol andfiltered hot to remove an insoluble product. The dye solution wastreated with an equal volume of 2% aqueous potassium iodide solution andthe resulting fiocculent dye precipitate was filtered 01f, washed withwater, ether, then isopropyl alcohol and dried at 64 C.

The melting point of the dye Was 197-200 C.

EXAMPLE VI 3,9-Diethyl-5-1/Ieth0xy-3'- (a-Tlzienylmethyl)Selenathiacarbocyanine Iodide 0.65 gram of 2-methyl-3-(a-thienylmethyl)benzothiazolium bromide and 0.75 gram of 3-ethyl-5-methoxy-2-[Z-(methylthio) 1 butenyl] benzoselenozolium iodide were stirred up in20 mls. of boiling iso-propyl alcohol. 2 mls. of triethylamine were nextadded and the resulting purple solution was heated at the boil for 5minutes during which time crystals having a green reflux separated outin the Walls of the reaction vessel. After cooling 15 minutes to roomtemperature with constant stirring, the solid was filtered oil and thenboiled up with 250 mls. of methyl alcohol. The boiling solution wasfiltered and the residue discarded. The filtrate was evaporated to avolume of mls. and cooled to 5 C. The dye crystals which separated outwere filtered off, washed with ether, and dried at 65 C. The meltingpoint of the dye was 198 C.

EXAMPLE VIII 5 -Chl0r0-3-Ethyl-4 -M ethyl-3 oc-ThienylmethylOxathiazolocarbocyanine Iodide 0.25 gram of2,4-dimethyl-3-(a-thienylmethyl) thiazolium iodide, and 0.25 gram ofZ-B-acetanilidovinyl-S-chloro-3-ethylbenzoxazolium iodide were refluxedin 5 mls. of iso-propyl alcohol. Ten drops of triethylamine were nextadded, resulting in the immediate formation of a pink solution. Thereaction mixture was boiled 1 minute with stirring and then allowed tocool to room temperature while maintaining agitation. The orange-pinkcrystals which had come down shortly after heating were thencentrifugated. The solid was triturated with cold acetone, filtered andthen recrystallized from 10 mls. of methyl alcohol. The yield of dyemelting at 2162l8 C. amounted to 50 milligrams.

5 I claim: 1. A sensitizing dye intermediate of the following formula:

2. A sensitizing dye intermediate of the following formula: 15

3. A sensitizing dye intermediate selected from the group consisting ofthose having the following formulae:

wherein X is an anion.

References Cited in the file of this patent UNITED STATES PATENTS

3. A SENSITIZING DYE INTERMEDIATE SELECTED FROM THE GROUP CONSISTING OFTHOSE HAVING THE FOLLOWING FORMULAE: